1. Field of the Invention
The invention relates in general to a signal transmitter, and more particularly to a signal transmitter having a deskew function.
2. Description of the Related Art
Data transmission between electronic elements is usually achieved through changing or coupling/conducting data signals on conducting lines. Data transmission of a group of multiple data bits simultaneously completed through multiple transmission channels is referred to as parallel transmission. On the other hand, data transmission of data bits transmitted one after another through one single transmission channel is referred to as serial transmission.
Compared to serial transmission, parallel transmission is in general faster, and is more commonly applied to environments with shorter transmission channels between electronic elements. For example, data transmission between integrated circuits on a printed circuit board and data transmission between a printer and a personal computer mostly adopt parallel transmission. Long-distance parallel transmission may be affected by signal propagation delay differences between the parallel channels. In the occurrence of such signal propagation delay differences, multiple data bits that are expectedly to simultaneously arrive at a destination are often caused to arrive at a destination receiver at different time points. Differences in the arrival time are referred to as skew in the technical field.
For shorter transmission channels or moderate transmission speeds, the skew barely results in noticeable effects and can be neglected. However, as the transmission channel gets longer or the transmission speed increases, quantitative values and differences of such signal propagation delay may become quite apparent, hence an increase in the skew. With an excessive skew, a data bit originally belonging to a particular byte may be erroneously considered as a member of a previous or next byte, leading to a data transmission error.
In a convention approach for processing the skew, differences of signal propagation delays of individual channels at a receiver are first identified, i.e., offset values of the individual channels, and temporal compensations are then correspondingly provided at the receiver. For example, for a transmission channel that has a shorter signal propagation, delay is first provided with an additional signal delay by a filter at a receiver, such that the data bits in the transmission channel are regarded as being received at a later time point. Thus, a deskew function can be achieved at the receiver.